Billing is done per hour. Each month has a 672 hour (28-day) billing cap with server runtime past that point being free of charge. DigitalOcean accepts payments via Visa, MasterCard, American Express, Discover, and PayPal.

Automatic backups can be made for 20% of the droplet price and an unlimited amount of snapshots at $0.02 per GB of storage can be made manually.
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DigitalOcean has a control panel that's intuitive and easy to use, new servers (Droplets) can be spun up in under a minute and they offer stock "apps" (LAMP, RoR, Wordpress) that can be deployed instantly. There's also an extensive documentation for people new to VPS.

Quick and knowledgeable customer service, extensive documentation and helpful community.